1. Technical Field of the Invention
The present invention relates to a disk drive used for recording or reproducing data on or from a disk including a substrate made from a high polymer material. In particular, the present invention relates to a disk drive including a head slider having a configuration optimum to record or reproduce data on or from a disk including a high polymer substrate.
2. Description of the Prior Art
Along with the recent growth of information processing technology, it has become increasingly necessary to develop disk drives capable of realizing large recording capacities and high-speed recording/reproducing of data. In particular, magnetic disks and magneto-optical disks, which can be manufactured on large scales at low costs, are expected to be used not only for large-sized computers and personal computers, but also for devices to meet requirements of the recent multi-media age, such as image/audio communication systems, facsimile transmitters/receivers, printers, displays, image displays, and other information memories associated with various apparatuses.
Of various disk drives, such as a magnetic disk drive, a magneto-optical disk drive, and an optical disk drive, the magnetic disk drive is most popular. A configuration example of such a magnetic disk drive is shown in FIG. 1. Referring to FIG. 1, the magnetic disk drive includes a housing 101, a spindle motor 102, and a magnetic disk 200 rotated by the spindle motor 102. In operation of the magnetic disk drive, a head slider 104 is located at a desired position on the magnetic disk 200 by a movable actuator 103, to allow a head mounted on the head slider 104 to write or read data on or from the magnetic disk 200.
The housing 101 made from an aluminum alloy, a hard plastic resin, or the like has a substantially flat upper surface on which the spindle motor 102 is disposed.
The spindle motor 102 is configured as a flat brushless motor, which is driven with its angular velocity controlled at a constant value for rotating the magnetic disk 200 in the direction R1.
The magnetic head mounted on the head slider 104 is flied in such a manner as to face to the disk, to write or read data on or from the disk. The head slider is driven by the movable actuator 103. A configuration of the movable actuator 103 is shown in FIG. 2.
The movable actuator 103 shown in FIG. 2 includes the flying type head slider 104, an elastic member 105 for supporting the head slider 104, an arm 106 for supporting the elastic member 105, a vertical shaft 107 for movably supporting one end of the arm 106, and a motor 108 for turning the arm 106 around the vertical shaft 107.
An air flow passage, allowing flow-in/flow-out of air, is formed in the back surface of the head slider 104 and, upon rotation of the magnetic disk 200, the head slider 104 is flied from the surface of the magnetic disk 200 with a slight spacing formed between the back surface of the head slider 104 and the front surface of the magnetic disk 200. In such a state, data is written on or read from, that is, recorded on or reproduced from, the magnetic disk 200 by the head mounted on the head slider 104.
The flight height of the head slider has been generally set in a range of about 0.1 xcexcm or less; however, it tends to become gradually smaller along with the increased capacity of a magnetic disk. At present, a disk drive with the flight height reduced to a value in a range of about 20 nm to about 40 nm is being developed.
The arm 106, which is made from a rigid material, is turned around the vertical shaft 107 to move the head slider 104 in the radial direction R3 (see FIG. 1) of the magnetic disk 200 for seeking operation, so that the magnetic head mounted on the head slider 104 accesses a desired track of the magnetic disk 200.
The motor 108 includes a voice coil 109 mounted to the other end of the arm 106, and a magnet 110 fixed on the housing 101. A drive voltage is supplied from an external source to the voice coil 109, to drive the voice coil 109 in the direction R2.
When a drive current is supplied from an external source to the voice coil 109, the arm 106 is turned around the vertical shaft 107 on the basis of a force generated by a magnetic field of the magnet 110 and a current flowing in the voice coil 109. As a result, the head slider 104 mounted to the other end of the arm 106 is moved substantially in the radial direction of the magnetic disk 200 as shown by the arrow R3 in FIG. 1, and the magnetic head mounted on the head slider 104 records or produces information on or from a specific track of the magnetic disk 200.
A detailed configuration of the head slider 104 is shown in FIG. 3. The head slider 104 retains a magnetic head 301 as a recording/reproducing element at a position close to the disk, and causes the magnetic head 301 to write or read signals on or from the disk. A surface, facing to the disk, of the head slider 104, that is, the upper surface of the head slider 104 in FIG. 3 has rails 302 which receive the pressure of air flowing between the head slider 104 and the disk, thereby slightly flying the head slider 104 from the disk. The related art head slider 104 is generally formed into a rectangular parallelopiped shape having a width W of 1.6 mm or more, a length L of 2.05 mm or more, and a height H of 0.43 mm or more.
FIG. 4 is a conceptual view showing a state that the head slider 104 is flied from the disk 200 for allowing the head to write or read data on or from the disk 200, and also showing an air flow generated on the surface of the disk. The head slider 104 is supported by the elastic member 105, which is in turn supported by the rigid arm 106. The head 301 is fixed to the tip of the head slider 104. The disk is rotated in the direction shown by an arrow from the arm 106 side to the head slider 104. In this case, as shown in FIG. 4, an air flow based on the viscosity of air is generated on the surface of the disk, and accordingly the head slider 104 is controlled by the air flow to be slightly flied from the surface of the disk 200, and in such a state, the head slider 104 causes the head 301 to write or read data on or from the disk 200.
A general structure of a magnetic disk used for a magnetic disk drive will be described with reference to FIG. 5. Referring to FIG. 5, the previously proposed magnetic disk 200 has an under layer 202, a magnetic recording layer 203, and a protective layer 204 sequentially formed on each of polished front and back surfaces of a substrate 201 made from an aluminum alloy or glass.
The substrate 201, which has been mainly made from an aluminum alloy or glass, is to be made from a high polymer material such as polycarbonate, polyolefin, polystyrene, or poly methyl methacrylate (PMMA) and is widely available not only for magnetic disks but also for magneto-optical disks.
The disk having such a configuration differs in rigidity depending on the kind of substrate material and may cause various kinds of deformation in service environments. For example, the mounting configuration of the disk to a spindle motor by using a damper gives stress to the disk, which may cause distortion and waviness, and high-speed rotation of the disk causes the runout of the disk surface at the outer periphery. In particular, the disk including a high polymer substrate tends to cause large waviness and large runout of the disk surface.
On the other hand, as described above, the flight height of a head slider from the surface of a disk has been required to be reduced to 0.1 xcexcm or less, and recently, to the order of about 20 nm to about 40 nm. To realize such a flight height, the surface of a disk made from an aluminum alloy or glass is polished during the manufacturing process of the disk for improving the smoothness of the surface of the disk; however, it is difficult to polish the surface of a disk including a substrate made from a high polymer material such as polycarbonate, polyolefin, polystyrene, or PMMA during the manufacturing process of the disk and, therefore, it is difficult to ensure the smoothness of the surface of the disk including a high polymer substrate comparable to that of the disk including the aluminum or glass substrate.
In addition to the above-described problem with surface smoothness, the disk including a high polymer substrate presents another problem in that distortion occurs easily over the entire disk surface, as compared with the disk including the substrate made from an aluminum alloy, glass or the like. For example, in manufacture of the disk including the glass substrate, a radius of curvature over the front surface of the disk can be made in the order of about 30 m. On the contrary, for the disk including a substrate made from a high polymer material such as polycarbonate, polyolefin, polystyrene, or PMMA, it is impossible to manufacture the disk having a large radius of curvature over the front surface of the disk. For example, part of the disk sometimes has a radius of curvature being as small as about 10 m to about 20 m. More concretely, the disk has a radius of curvature ranging from 10 m to 20 m in the radial direction, and a radius of curvature ranging from 20 m to 30 m in the circumferential direction.
To realize high density recording/reproducing of data, it is required to make a head slider operate closer to a disk, that is, reduce a spacing between the head slider and the disk. In the case of flying the head slider against a disk including a high polymer substrate, which is poor in flatness, however, the reduction in spacing between the head slider and the disk raises the possibility that the head slider comes in contact with the disk, and accordingly, it is difficult to ensure a small spacing similar to that between the head slider and the disk including the aluminum or glass substrate.
The present invention has been made to solve the above-described problems of the related art disk drive, and an object of the present invention is to provide a disk drive using a disk including a substrate made from a high polymer material, which is capable of reducing a spacing between a head slider and the disk to a value comparable to a spacing between the head slider and a disk including an aluminum or glass substrate.
Another object of the present invention is to provide a disk drive of the present invention, which is capable of recording data on a disk including a substrate made from a high polymer material at a density higher than that obtained by using a related art disk drive by reducing a spacing between a head slider and the disk formed with a high polymer substrate.
To achieve the above objects, according to a first aspect of the present invention, there is provided a disk drive including: a disk including a substrate made from a high polymer material; a head flied from the front surface of the disk upon rotation of the disk for recording or reproducing data on or from the disk; and a head slider on which the head is mounted; wherein the head slider is formed into an approximately rectangular shape and is specified such that a width W along the direction substantially parallel to the radial direction of the disk is in a range of 0.5 mm to 1.5 mm, and a length L along the direction substantially parallel to the circumferential direction, that is, the rotational direction of the disk is in a range of 0.5 mm to 1.8 mm.
In the above disk drive of the present invention, preferably, the head slider is mounted on an elastic supporting member constituting an actuator movable substantially in the radial direction of the disk in which a surface, facing the disk, of the head slider has a projection which projects on the front surface side of the disk, the projection being configured as two rails symmetrical in the width direction of the head slider with respect to the longitudinal axis of the head slider; and the head is mounted to the tip or its neighborhood of at least one of the rails, the mounting position of the head being either a central portion of the rail in the width direction parallel to the width direction of the head slider or a position offset inwardly from the central portion of the rail to the center of the head slider in the width direction.
In the above disk drive of the present invention, preferably, the head slider is mounted on an elastic supporting member constituting an actuator movable substantially in the radial direction of the disk, in which a surface, facing the disk, of the head slider has a projection which projects on the front surface side of the disk, the projection being configured as an island rail formed at a central portion of the head slider in the width direction; and the head is mounted to the tip or its neighborhood of the rail, the mounting position of the head being a central portion or its neighborhood of the rail in the width direction parallel to the width direction of the head slider.
In the above disk drive of the present invention, preferably, the head slider has a length L in a range of 1.25 mm or less.
In the above disk drive of the present invention, preferably, the disk is configured as a disk including a substrate made from either of polycarbonate, polyolefin, polystyrene, and poly methyl methacrylate (PMMA).
In the above disk drive of the present invention, preferably, the disk is configured as a disk including a high polymer substrate in which a radius of curvature in the radial direction is in a range of 10 m to 20 m, and a radius of curvature in the circumferential direction is in a range of 20 m to 30 m.
In the above disk drive of the present invention, preferably, the disk is configured as a disk including a high polymer substrate in which a glide height is in a range of 15 nm or less.